1. Field of the Invention
The invention relates to a water treatment system and method and, more particularly, a water treatment system and method having improved dosing control for accurate distribution of treated water.
2. Description of the Related Art
High purity water is required for many applications including, for example, in chemical and biological analytical laboratories. Water for these applications is purified by a number of well-known techniques, including filtration, single or multiple distillation, sorption, and ion exchange. Water initially treated by distillation or reverse osmosis filtration is often further purified (polished) by passage through activated carbon beds to adsorb residual contaminants, principally organics. The pretreated water may also be treated by passage through layered or mixed beds of ion exchange resins to remove residual ionic impurities. Often, these water streams are also filtered through microporous filters to remove further residual contaminants prior to the system outlet.
When purified water is not required, conventional water treatment systems typically recirculate the water in a continuous or periodic operation through the various water treatment devices included in the system, for example UV lamps, ion exchangers and ultrafilters, to prevent the water quality from deteriorating while standing. Because of the high energy costs incurred during continuous operation of a recirculation pump or the like, and the associated high noise levels which can be disturbing to nearby workers, water treatment systems are often operated in a periodic mode of, for example, about 50 minutes standstill and 10 minutes of recirculation through the system. When purified water is required, therefore, it is sometimes necessary to circulate the water through the system for a period of time before the water can be used.
In addition, control of the purified water flow rate from the system is typically performed by adjusting an outlet valve. However, because the conventional system pump operates at a single high speed and output rate, to achieve the highest flow rate at the outlet valve, it can be difficult for users to dose small and/or accurate quantities of purified water from these systems.